The present invention relates generally to voltage regulators, and more particularly to control systems for switching voltage regulators.
Voltage regulators, such as DC to DC converters, are used to provide stable voltage sources for electronic systems, particularly electronic systems that include integrated circuits. Efficient DC to DC converters are particularly needed for battery management in low power devices, such as laptop notebooks and cellular phones, but are also needed for higher power demand products, e.g., desktop computers or servers. Switching voltage regulators (or more simply “switching regulators”) are known to be an efficient type of DC to DC converter. A switching regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and filtering the high frequency voltage to generate the output DC voltage. Typically, the switching regulator includes a switch for alternately coupling and de-coupling an unregulated input DC voltage source, such as a battery, to a load, such as an integrated circuit. An output filter, typically including an inductor and a capacitor, is coupled between the input voltage source and the load to filter the output of the switch and thus provide the output DC voltage. A controller measures an electrical characteristic of the circuit, e.g., the voltage or current passing through the load, and sets the duty cycle of the switch in order to maintain the output DC voltage at a substantially uniform level.
Voltage regulators for microprocessors are subject to ever more stringent performance requirements. One trend is to operate at ever lower voltages, e.g., less than 1 volt, and at higher currents, e.g., 50-150 amps. Another trend is to turn on or off different parts of the microprocessor in each cycle in order to conserve power. This requires that the voltage regulator react very quickly to changes in the load, e.g., several nanoseconds to shift from the minimum to the maximum load, and to have a fast transient response, e.g., to quickly stabilize without significant voltage or current ripple.
Still another trend is to place the voltage regulator close to the microprocessor in order to reduce parasitic capacitance, resistance and/or inductance in the connecting lines and thereby avoid current losses. However, in order to place the voltage regulator close to the microprocessor, the voltage regulator needs to be small and have a convenient form factor.
In addition to these specific trends, high efficiency is generally desirable in order to avoid thermal overload at high loads and to increase battery life in portable systems. Another desirable feature is for the voltage regulator to have a “standby mode” which consumes little power at low loads.